linux-kernel - Re: OOM notifications

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Message-ID: <20071026173550.333d8eb4@bree.surriel.com>
Date:	Fri, 26 Oct 2007 17:35:50 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Martin Bligh <mbligh@...igh.org>, marcelo@...ck.org,
	linux-kernel@...r.kernel.org, drepper@...hat.com,
	linux-mm@...ck.org
Subject: Re: OOM notifications

On Fri, 26 Oct 2007 14:11:12 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> Sure, but in terms of high-level userspace interface, being able to
> select() on a group of priority buckets (spread across different
> nodes, zones and cgroups) seems a lot more flexible than any
> signal-based approach we could come up with.

Absolutely, the process needs to be able to just poll or
select on a file descriptor from the process main loop.

I am not convinced that the magic of NUMA memory distribution
and NUMA memory pressure should be visible to userspace.  Due
to the thundering herd problem we cannot wake up all of the
processes that select on the filedescriptor at the same time
anyway, so we can (later on) add NUMA magic to the process
selection logic in the kernel to only wake up processes on
the right NUMA nodes.

The initial patch probably does not need that.

-- 
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan
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